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Old 12-16-2008, 02:24 PM   #1
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Basement - Rigid Insulation/Extruded Polystyrene

I am planning to insulate my basement and rim joists with rigid/extruded polystyrene. I just found out about the foil-faced variety and was wondering if there is an advantage/disadvantage to using one over the other. Any help would be appreciated. Thanks.


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Old 12-16-2008, 02:51 PM   #2
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The foil faced has high R value but isn't as easy to cut. The polystrene can be scored and snapped. I use a small hand saw and straight-edge to cut the foil faced.


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Old 12-16-2008, 02:55 PM   #3
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Cut the rigid foam slighly small and seal the edges with the expanding foam that also works as an adhesive.

I pre-cut my foam small, foamed the rim joist/sill and others and then pushed in the rigid back to the rim joist while it was still sticky. Then I just used some fiberglass to fill the remaining void.

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Old 12-16-2008, 03:52 PM   #4
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Most foil faced foam boards are iso-cyanurate foam which will have a slightly higher R-value per inch than extruded poly-styrenes. There are some foil faced boards out there that are expanded poly-styrenes. This is the bead board that looks like cheap beer cooler foam. They are generally cheaper, lower performance materials. Whatever you use, foaming it in place with a low ex foam is a good idea.
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